The present invention relates to a toner cartridge and an electrophotographic printer employing the same.
A conventional electrophotographic printer is discussed in Japanese Utility Model Laid-Open Publication No. 1-97356.
This electrophotographic printer has a rotatable cylindrical stirring means in a hopper for containing developer therein (hereinafter referred to as a developer hopper) to prevent the so-called toner blocking phenomenon from occurring inside the developer hopper. The toner blocking phenomenon means that a mass or clump of toner is formed inside the developer hopper. A developer supply roller, which is driven by an external device, is provided at the portion adjacent to the lower end of the developer hopper. The stirring means contacts the developer supply roller so that it is driven by the developer supply roller.
However, this electrophotographic printer has a problem in that the effect involving in stirring the toner is relatively remarkably reduced when the developer hopper is formed as a cartridge.
An electrophotographic printer having a detachable toner container as the developer hopper has been developed. The so-called toner cartridge can be replaced with another toner cartridge in order to facilitate the supply of the toner or prevent the toner from scattering on other portions of the electrophotographic printer, such as the paper feed system, when the toner is supplied into the electrophotographic printer.
Replaceable toner cartridges are now sold for use in photographic printers of this type. Since the toner cartridge of this type is filled with toner at the factory when the electrophotographic printer is manufactured, it cannot be touched by user's hands in ordinary circumstances.
Accordingly, it was a serious problem that the toner cartridge, which is liable to be kept in a warehouse for a long time, is likely to suffer from toner blocking.
This toner blocking is liable to be caused by a mass of toner which forms in the toner cartridge during storage in the warehouse and which sticks to the inner wall of the toner cartridge, or all of the toner may simply form a large mass. If toner blocking occurs, the resistance of the mass of toner to the stirring means is generally remarkably increased. In particular, if the mass of toner adheres to the stirring means, it sometimes happens that the stirring means can not rotate even if it contacts the supply roller. If the stirring means does not rotate, the toner is not stirred, which causes anomalous abrasion of the developer.
There is another problem in that the user cannot take out the mass of the toner after inspecting the inside of the cartridge every time the cartridge is replaced with another one. Furthermore the frequency of the replacement increases if the amount of the toner in a toner cartridge is decreased to prevent toner blocking from occurring which causes an increase in the printing cost.